Lenticular screens have long been a means to provide the user with an autostereoscopic display allowing each eye to see a different perspective. The idea of using a corduroy-like lenticular screen and an interdigitated stereo pair was first enunciated in 1915 by Hess in U.S. Pat. No. 1,128,979, and there has been much art disclosed in the field since Hess.
Indeed, the idea of using lenticular screens with inward facing lenticules, which we employ in this disclosure, has been applied for years in the manufacture of rear projection television sets. It is the manner in which we use this configuration and improve upon it that leads to great improvements in image quality as will be described below.
When viewing a lenticular autostereoscopic display, the user does not wish to be aware of the structure or the presence of the screen. The user is concerned with seeing the image and does not wish to be subjected to any distraction. Such distractions are caused by the visibility of the lenticular screen structure itself. This is to some extent manifested by the visibility of the straight-line boundaries between lenticules, which appear to the eye as if they are (more or less) vertical going rulings. The finer the pitch of the screen, the less obtrusive this “virtual” ruling effect, but in some cases the pitch of the screen must remain large, and in all cases the problems of reflections from the surface remain, as described next.
With the lenticules facing outward, as is typical, the user is aware of the “ruling” structure as well as a considerable amount of reflection of ambient light. Annoying reflections occur at the surface of the lenticular screen. This phenomenon arises from the (more or less) horizontal refractive nature of the corduroy-like lenticular columns that create a myriad of reflections spreading across the surface of the screen.
These reflections interfere with the intelligibility of the displayed image as well as detract from the enjoyment of viewing the display. An anti-reflection (AR) coating can be difficult to apply to a surface made up of miniature lenticules. AR coatings are usually coated on smooth and continuous surfaces, and not on the corduroy-like surface of the lenticular screen.
Another problem related to the unimpaired viewing and even the intelligibility of the display has to do with the need to switch between planar and stereo states. For certain applications, especially desktop applications, the user of a lenticular autostereoscopic display may well wish to work on a word processing application or e-mail at one moment, and the next he or she may wish to see a stereoscopic image. It has been observed and understood that an application consisting of alpha numerics can become unintelligible when viewed through a lenticular screen because of its refractive properties.
If one wishes to display information on this autostereo device, the information must be formatted to accommodate the properties of the lenticular screen. In such a case, the image must be dissected into columns and within such columns, image stripes, or the user will observe an image that is garbled and unintelligible. The information, specifically alphanumerics of small to normal font size, or task bars and dialogue boxes and the like, will be difficult for the user to read. In order to cure this viewing problem, the user could remove the lenticular screen and then replace it when it is time to display stereo formatted information.
For this reason, it would be desirable to be able to “deactivate” or “neutralize” the refractive properties of the lenticular screen. One approach, as mentioned above, is to remove the screen entirely when viewing in the planar mode. But this can be cumbersome and might not meet with favor on the part of users. In addition, there is an alignment problem that might be difficult to solve since the juxtaposition of the lenticular screen and the display screen needs to be accomplished with extreme precision. But even if the problem can be solved with some pin registration system, or some other means of calibration, we are left with a solution to the problem that is intrinsically cumbersome. Even the embodiment disclosed by Eichenlaub in U.S. Pat. No. 5,500,765, clever as it is, requires the addition or removal of a lenticular screen with negatively-shaped lenticules, the purpose of which is to neutralize the refractive properties of an in-place lenticular screen.
The present disclosure takes advantage of inward facing lenticules that provide the same refractive properties as that of a lenticular screen with outwardly facing lenticules. By having the lenticules face inwardly toward the display screen, we are able to achieve a lenticular autostereoscopic display with greater clarity in the stereo mode, and thus with an enhanced sensation of image quality and depth. Inward facing lenticules makes the boundary “virtual” ruling effect disappear and allows the provision of a standard quality AR coating to the outwardly facing flat surface.
We also describe means to neutralize the refractive properties of the screen by automatic means rather than by cumbersome efforts on the part of the user. By automatic, we mean that with the push of a button, the user will be able to select between autostereo and stereo modes with optimized optical properties and clarity of image. Even better, with the change of content from stereo to planar, the unit will automatically activate or deactivate the lenticules' refractive properties.